1. Field of the Invention
The present invention relates to a malfunction detecting apparatus for on-vehicle charging systems, which ensures accurate detection as to whether or not a charging line from a generator to a battery on a vehicle has come off from the generator.
2. Description of Related Art
In general, detecting the disconnection of a charging line connecting a generator and a battery on a vehicle is one of the significant items for vehicle control. Concerning this detection, some methods have already been provided. For example, such a method is known for a system having a sensing line for detecting battery voltage, wherein battery voltage and generator voltage are compared. When the battery voltage is much lower than the generator voltage, it is determined that the charging line has come off (or slipped off or put out of the connection). However, a current mainstream trend is to use a system wherein wiring such as a sensing line is not employed. In such a system, the above method that requires the sensing line is not applicable.
For a system having no sensing line, a method is known, as disclosed in Japanese Published Unexamined Application No. 2002-027796, wherein a ripple waveform of an on-vehicle generator is used to detect the coming-off condition of a charging line.
Further, for a system in which voltage to be generated is controlled by a regulator in response to a voltage command transmitted from an engine ECU (electronic control unit), a method disclosed in Japanese Published Unexamined Application No. H08-079981 is known. With this method, battery voltage detected by the engine ECU is compared with a command value for generation. And, when a difference between the battery voltage and the command value is more than a threshold, the generator is determined as being in failure.
The method disclosed in Japanese Published Unexamined Application No. 2002-027796 set forth above, however, has a difficulty in determining between malfunction and normal function at the time of high loading when ripples are large in a normal state (i.e. a state where a charging line has not come off, or at the time of low loading when ripples are small in a malfunction state. Such a difficulty is problematic in performing accurate detection.
The method disclosed in Japanese Published Unexamined Application No. 08-079981 set forth above enables detection of any malfunction that a generator is involved in. However, the problem is that it is difficult to determine with this method whether the malfunction is caused by the failure of the generator or simply caused by the coming-off of a charging line.